1. Field of the Invention
The present invention relates to a skirt for a toner cartridge, and more specifically relates to a skirt having a preselected geometry for use with a toner cartridge in order to inhibit creep and promote efficient movement of toner within an electrophotographic (laser) printer.
2. Description of the Related Art
Laser printers utilize a light beam which is focused to expose a discreet portion of an image transfer drum in a further attempt to attract printing toner to these discreet portions. Toner comprises a mixture of pigment, typically carbon black, and plastic. When the toner becomes electrostatically charged, the toner is attracted to exposed portions of the image transfer drum. When a medium, printing paper, passes over the rotating transfer drum, the toner is transferred to the medium. Afterward, the medium passes through a heat fuser so that the plastic is melted and permanently fused with the medium.
Existing laser printers utilize replaceable toner cartridges having a developer roll, a toner reservoir and a metering system. Within the toner cartridge a skirt is connected to a rotating shaft in order to define a paddle which moves the toner through one or more reservoir areas and toward the image transfer drum. The skirt sweeps and/or flicks toner from one portion of the cartridge to a second portion of the cartridge. After repeated operations, the toner becomes depleted due to the printing process.
There are generally three factors that influence a skirt's ability to transport toner: length, geometry and thickness. In order to work properly, the skirt must engage portions of the toner cartridge housing and must deflect to some extent for best moving the toner. However, one problem encountered during shipping of toner cartridges occurs when the cartridges are subjected to elevated temperatures of greater than 100 degrees Fahrenheit. When the skirt is subjected to such temperatures and deflected due to engagement with some portion of the toner cartridge housing, the deflection combined with the high temperatures can result in a permanently deflected skirt, which is typically referred to as “creep” of the material. A skirt which has been affected by creep is less effective in moving toner as it provides less interference with the housing and thus is limited in the amount of toner which can be transferred toward a desired location in the toner cartridge. When the skirt fails to provide an adequate amount of toner, then starvation occurs resulting in an incomplete print image or an image which is lighter than desired.
Software solutions have been implemented to position the skirt at a location with decreased or no contact with the toner cartridge when the cartridge is shipped or between operating cycles. However, such solution resulted in a decrease in throughput of media since the skirt was repositioned between each media page printed. With the detrimental effect to printing functionality, a mechanical solution was desirable.
It would be desirable if a skirt design limited or eliminated creep associated with toner cartridge paddles.